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1  Topics / Robotics / Re: Build quad robot - Questions on: June 20, 2013, 06:02:35 am
As mentioned Hobby king et al
Brush-less motors (you want out runners) ARE bi-directional (but you can also use counter-rotating props = all motors trun same way)
For motor control, use ESCs (over spec them)
Personally I would start with a ready-made flight controller to test my airframe
http://www.pyramidmodels.com/shop/product.php/866/fully_assembled_kk_multicopter_control_board_blackboard_v5_5 etc.

Once I have faith in the airframe, I would then start to play (as I am)

Remember you have to balance airframe weight against motor/prop dynamics against battery specs (prob. at least 2.2Ah 20C discharge 3S) to arrive at a sensible flight time.

This may help
http://www.ecalc.ch/xcoptercalc.htm?ecalc&lang=en

Have fun
2  Using Arduino / General Electronics / Re: first pcb try on: February 17, 2013, 04:35:37 pm
Some nice attempts. Tinning makes a massive difference to the solderbility.

A little while ago, I came across an article, but can't find it right now. It used a CD printer to print the etch resist and the silk screen layers directly onto the board, pretty nifty. I think they used a simple two-edged jig to ensure registration. They were using a non-FeCl etch too (which is a pain to recycle and stains everything around).
Use good quality PCB drill bits and a drill post (dremel et al make them). If you allow the drill to self-centre, drilling is quite easy and can look good. Self centring requires the pad hole to be quite small). The technique is to visually align the drill/work, then as the drill nears the work, allow the work to move, and the hole in the pad will align with the drill, hold firmly and press through. Obviously works with smaller boards. Use of backing board leaves a good finish.
3  Using Arduino / Programming Questions / Re: GPS direction/ distance problems on: February 17, 2013, 03:38:19 pm
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You could be travelling backwards, looking toward your original location, but the GPS would not know this, it would display you moving toward your destination.
No, it wouldn't. It would show a vector moving away from the target. Now, it would not know, or care, which way you are facing, or whether you are moving in the direction you are facing, or not. All it knows is which way you are moving.
Indeed, re-read smiley
4  Using Arduino / Programming Questions / Re: GPS direction/ distance problems on: February 17, 2013, 12:12:30 pm
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A GPS tells you where you are, not which way you're looking (difficult to tell from 18 000km away)
It can tell you which way you are going, when you are moving, based on a vector between two locations (the current one and the previous one). The GPS on my trike tells me that. But, it hasn't a clue when I'm parked in the driveway.
to expand. You could be travelling backwards, looking toward your original location, but the GPS would not know this, it would display you moving toward your destination. This is why you need a compass to give you rotational information.
Yes, you can use breakout boards.
It is also useful to have a compass to indicate that the vehicle has turned sharply if you are tracking position on a map, as it will update much faster than the GPS. (rotation is more likely to be a change of course than a spin). Using GPS alone results in jerky updates. This is part of the reason for your TomTom et all having a digital compass. Once moving, the unit can infer absolute direction and so North can quite easily be displayed without a compass. Also not that GPS displays tend to follow roads rather than position. This can be observed by deviating from the programmed route onto a parallel route. The display will keep you on the route until you're just too far away for it to be correct, at that point the display will jump.
 
BTW you would normally have a compensation program to allow the compass to compensate for local magnetic anomalies, this usually consists of making several 360 rotations. My HTC asks me to make figure of eight movements.
5  Using Arduino / Project Guidance / Re: Simple DC motor + IR sensor on: February 16, 2013, 06:17:55 pm
you need a flag smiley-wink
It's like a paint spray that say's...." I've sprayed"

boolean sprayFlag = LOW;

only spray if the flag is low, when you spray, set the flag high.

Some other criteria will set it low again
6  Using Arduino / Programming Questions / Re: GPS direction/ distance problems on: February 16, 2013, 05:54:21 pm
You need a compass too
7  Using Arduino / Project Guidance / Re: Active Lowpass Filter for PWM to DC to control a Photomultiplier on: February 15, 2013, 08:41:32 am
Does this solution help?
here

This IIC version of the pot may be nicer, with a 10bit resolution
8  Using Arduino / General Electronics / Re: GEHCT - Green Energy Human Cheap Transport on: February 15, 2013, 06:59:33 am
I have to say, this is the best "do it for me" kit that I've seen so far smiley-wink

This guy is the dogs doodaas on the subject, see what he has to say.
9  Using Arduino / Project Guidance / Re: solar tracker using RTC on: February 15, 2013, 06:49:13 am
Sorry AMPS-N, couldn't help myself smiley-wink
You have painted yourself into a corner, it will have to be calculated then, but you will have to compromise on "cheapest". Leap years can be handled with a counter, but you will need to keep at least some variables in NVM.
keep us posted.
10  Using Arduino / Project Guidance / Re: solar tracker using RTC on: February 15, 2013, 06:39:28 am
Snap AWOL.

However, we may be forgetting about the Bangalore Tracker Crapper, these little birds are very well know for their preference to relieve themselves on the western most side of any solar tracking device! During the days of the Raj they caused untold problems!  smiley-eek
11  Using Arduino / Project Guidance / Re: solar tracker using RTC on: February 15, 2013, 06:34:49 am
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For LDR it require periodic maintenance.
I thought I was lazy! If it's just dust, who cares? The performance would effect both devices! But you could build in an auto calibration routine.
12  Using Arduino / Project Guidance / Re: solar tracker using RTC on: February 15, 2013, 06:11:18 am
Unless you really want to calc the sun's position, as suggested below, track the sun.
I would think that 4 LDRs would be cheaper than a RTC, the code smaller and as pointed out, accuracy is of no concern, it just tracks. Simpler still if you use a N/S mount as you only need 2 LDRs, and your single actuator. "darkness" is used to reset to the morning sun.

IDK, but tracking may also provide more power from reflected light in times of cloud cover as the sensor, being a heliotrope would point to the brightest part of the sky, not where it thinks the sun is.

[edit]in fact, at Nick Gammon pointed out, you don't need a constant sun location if using a simple N/S mount and single actuator! All  you need is (usable) sunrise and day length (1 byte would do, since you will not get 15hrs of usable sun) You may also have mountain/hill/building shadow to contend with . You may also need to adjust for apparent sun speed. You then move your actuator, starting at the correct time, at the correct speed for any day. Personally LDRs would be my choice - simples![/edit]
LDR Sealed type
Tracker
13  Using Arduino / Project Guidance / Re: Clean and energy efficient LED dimming on: February 14, 2013, 05:57:34 pm
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Hm, a resistor at the gate? I have the 4.5Volt at the LED even with the gate not connected to the Arduino.
To test. disconnect from the Arduino and tie the gate to ground using your pull-down resistor. You can short it to ground if you like. Check if you still have 4.5V

Quote
Source voltage? You mean the 12Volt that go to the LED? The IRLU8726PBF is made for up to 30Volt.
Sorry, that is fine, what I meant was do you have the correct limiting resistor for your LED for the voltage being supplied?

Are your grounds okay? Short, connected to a single point. Is your CAT6 shielded? and if so, is the grounding at a single point - it's not unusual for Radio2 to take control of your circuit smiley-wink If you have wires spanning the house, you will have quite a nice antennae going. Look out for the WOW! signal smiley-wink
14  Using Arduino / Project Guidance / Re: Heart-rate measurement using Arduino on: February 14, 2013, 11:17:40 am
Have you checked this site (go to root before searching) or googled?
15  Using Arduino / Programming Questions / Re: speedometer code using to photosensors for arduino on: February 14, 2013, 09:21:23 am
You may want to use uS rather than mS, depends on your apparatus, but it will give you better resolution. Taking g and your distances, how quickly do you anticipate your droplet passing between the gates?
is it usual to measure in m/s  rather than cm (which i think are only valid in dressmaking)/s?

Did you write this code?

If you don't have a board, download a simulator for now.
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